After the installation of our test equipment, the first goal was to get an overview of the infrared transmission behaviour.\\
Considering a scenario with a passive eavesdropping attacker, several questions arise:

\begin{enumerate}
 \item Is it necessary for the attacker to be in the line of sight?
 \item What is the angle of radiation?
 \item How far can the attacker be apart of the sender?
 \item Is it possible to catch the signal via reflections?
 \item What is the influence of other light sources (natural/artificial)?
\end{enumerate}
Regarding these questions, we conducted a series of experiments in order to find apposite answers.
Basically it is about receiving or not receiving a command from the sender at a certain point in space under some environmental conditions.\\
Thus, in order to accomplish the measurements, we first of all have to be able to correctly receive instructions from the remote control.

\subsection{Receiving}

As mentioned in Section \ref{sec:protocols}, devices from different manufacturers likely use differing protocols.
Since we aimed to perform some measurements with multiple remote controls, a main prerequisite was to be in the position to
detect incoming commands independent from the applied protocol.\\
Not reinventing the wheel, we made use the of the Infrared-Multiprotocol-Decoder from \cite{IRMP} that is a library for AVR microcontrollers,
enabling one to receive a wide list of different protocols like for example NEC, SAMSUNG, RC-5, RC-6 an many more.
As usual for embedded programming, we are limited by $\sim$32KB of Flash Memory. Therefore it is very useful to have the possibility to activate only those protocols
that one needs in order to save memory space.\\
As mentioned in Section \ref{sec:protocols}, every transmission starts with a burst, followed by a pause. Based on the durations of these periods,
one can almost uniquely determine which protocol will be applied and accordingly set the timing tables for the further reception process.\\
To compile and run the code on our Arduino platform, we however had to put into effect slight changes, which comprised
commenting out several lines as well as setting correct pin defintions for our receiver sensor.
\subsection{Angle of Radiation}

At first we were interested in which angle the infrared light is emitting from its sender LED. Therefore we wrote a small test script that gets notfied
via the serial interface from our Arduino board if a valid command arrived. The script has to be setup with:
\begin{enumerate}
 \item \textbf{NUM\_POINTS}, the number of different measuring points in space.
 \item \textbf{ANGLES\_PER\_POINT}, the number of different angles tested at each measuring point.
 \item \textbf{NUM\_SAMPLES}, the number of samples sent out per angle.
\end{enumerate}
After every angle switch, we manually tell the script that a new angle starts. Hence, we are able to record how many of the \emph{NUM\_SAMPLES} samples
arrived at a certain angle from the current measurement point.\\
Our first experimantal session took place outside on the soccer field to assure the absence of reflections. We placed the senders alternately on a stand 170cm afar
from the receiver and rotated in intervals of 5$^\circ$, beginning at 0$^\circ$. For every rotation we sent out 10 samples. The setup is depicted in Figure \ref{fig:outdor}.\\
For the senders we employed the following list of remote controls and associated protocols (Table \ref{tab:rcs}).
\begin{table}[h]
  \centering
  \begin{tabular}[h]{|c|c|}
    \hline
    \textbf{Manufacturer} & \textbf{Protocol} \\
    \hline
    \hline
    Windows RC & RC6 \\
    \hline
    SEG & NEC \\
    \hline
    Samsung & Samsung \\
    \hline
  \end{tabular}
  \caption{List of Remote Controls and according protocols.}
  \label{tab:rcs}
\end{table}

\begin{figure}[h]
 \centering
 \includegraphics[width=0.5\textwidth]{img/outdor.jpg}
 \caption{Experimantal setup on the soccer field.}
 \label{fig:outdor}
\end{figure}
The results were quite varying from device to device. The Samsung RC (Firgure \ref{fig:out1}) for instance showed a radiation spectrum of almost 90$^\circ$, whereas on the other hand,
the Windows gadget (Figure \ref{fig:out3}) was just receivable inside a 20$^\circ$ area and even not all of the samples arrived.\\
Another interesting effect shows up in the plot for the Samsung RC. Symmetrically left and right from the main radiation spectrum after a small gap, two small sectors
appear where the signal is again received correctly. This phenomena can be explained by the construction of the emitter LED, which is embedded in a kind of chassis
that itself reflects the infrared beam.\\
A detailed diagram of the outcomes can be inspected in Figures \ref{fig:out1}, \ref{fig:out2} and \ref{fig:out3}.
The red sign is representive for the position of the receiver.\\

\begin{figure}[h]
 \centering
 \begin{minipage}{0.32\textwidth}
  \includegraphics[width=\textwidth]{img/result_outdor_samsung.png}
  \caption{Samsung}
  \label{fig:out1}
 \end{minipage}
 \hfill
 \begin{minipage}{0.32\textwidth}
  \includegraphics[width=\textwidth]{img/result_outdor_SEG.png}
  \caption{SEG}
  \label{fig:out2}
 \end{minipage}
 \hfill
 \begin{minipage}{0.32\textwidth}
  \includegraphics[width=\textwidth]{img/result_outdor_windows.png}
  \caption{Windows}
  \label{fig:out3}
 \end{minipage} 
\end{figure}



\vspace{1cm}
Our second experiment, we conducted inside the building, once in the dark with closed shutters and once with the influence of daylight.
The experimental setup, as well as the dimensions of the room can be viewed in Figure \ref{fig:room}.\\

\begin{figure}[h]
 \centering
 \begin{minipage}{0.49\textwidth}
  \includegraphics[width=\textwidth]{img/room.png}
 \end{minipage}
 \hfill
 \begin{minipage}{0.49\textwidth}
  \includegraphics[width=\textwidth]{img/roompic.jpg}
 \end{minipage}
 \caption{Dimensions of the room and experimental setup.}
 \label{fig:room}
\end{figure}

Identically to the outdoor session, we placed sender and receiver 170cm apart from each other and triggered ten samples per angle.\\
The results can be inspected in Figure \ref{fig:lab1} for the dark and Figure \ref{fig:lab2} for the bright run. The small sectors represent the varying angles.
A completely filled, dark green sector means that all samples for this angle arrived successfully at our receiving sensor. As one can see, in the dark scenario, each
of the 360 samples was reveived as a valid command. The invasion of daylight impairs the conditions a little bit, so that we were not able to receive full ten samples from
every measuring angle.\\
However, as a main result from this experiment, we take that no matter in which direction the remote control is pointed, one is able to receive the transmission.
Of course, this only holds for a small enough room with walls, allowing reflection to happen, and not too intense influence of natural light. Nevertheless, this a very beneficial result in terms of our attacker scenario.\\


\begin{figure}[h]
 \centering
 \begin{minipage}{0.49\textwidth}
  \includegraphics[width=\textwidth]{img/results_lab_dark.png}
  \caption{Dark environment}
  \label{fig:lab1}
 \end{minipage}
 \hfill
 \begin{minipage}{0.49\textwidth}
  \includegraphics[width=\textwidth]{img/results_lab_bright.png}
  \caption{Bright environment}
  \label{fig:lab2}
 \end{minipage}
\end{figure}

\subsection{Distance}

Certainly, the distance in which an infrared signal can be received, strongly depends on the invasion and intensity of light, especially natural light.
Since we were not in possession of a precise photometer, just a very coarse sensor of our smartphones, we accomplished the distance measurement
in the usual scenario, a remote control is applied, namely inside a building and with unshuttered windows.\\
Having a line of sight connection between sender and receiver, we experienced successful transmissions up to a distance of \textbf{61m}
(location: MENSA, remote control: Samsung).\\
This was really a suprising result and again encourages our proposed attacker scenario.

\subsection{Distance-Radiation Combination}

Another experiment took place in the gym, where we varied the position of the sender in steps of 1m to the left and right (maximal 2m) and
also in steps of 1m to the front (maximal 3m). The angles ranged from a start position of 0$^\circ$ up to 180$^\circ$. The results are graphically illustrated in Figure \ref{fig:combi}.

\begin{figure}[h]
 \centering
 \includegraphics[width=\textwidth]{img/combi.png}
 \caption{Combination of distance and radiation measurement.}
 \label{fig:combi}
\end{figure}






